Category: Portable

Casing, boxes, and plugged holes

Dear ST4 backers,

This is not the post you’ve been waiting for.. not yet. But we’re close. Very very close.

Today the sample casing was completed.. and it’s on its way here. The casing is without silkscreen paint, but all the metal and powder coating is there. It comes furnished with metal impact standoffs to easily and reliably fit all the electronics. And as you can see the rear electronics can be fitted in two ways, for either:
– rack mount
– desktop

Powdercoated ST4 sample casing.

Powdercoated ST4 sample casing.

Just like we promised. In desktop form the holes on the bottom plate can be plugged. Cover caps are supplied for this. Note that we will ask whether you want the rack or desktop version when the time arrives. And yes, you can still easily switch from rack to desktop or vice versa.

Furthermore, the cardboard boxes were also delivered to our office!

Behold, the box. Behold the official ST4 logo!

Behold, the box. Behold, the official ST4 logo!

Firmware 1.0 is as good as finished. As planned, we succeeded in making LFO and modulation settings per instrument. We’ve included the option to sort 100+ long sample file names. We’ve hit a point where new features just eat a bit too much CPU and/or memory and that means we _have_ to finish up. We’re just doing testing right now, and adding presets!

No telling when the big moment will be there. November seems pessimistic, while mid september seems optimistic. It all depends on if the electronics fit in right away, or we need to move some bits around. The silkscreen paint jobs _seem_ trivial right now, but with the Sawbench, for instance, the color was a big issue for the previous factory. Digital printing turned into silkscreen and in the end that delayed things by 4 weeks.. But we choose quality!

We’re sorry for the delay. We especially underestimated the casings. This is not a small or simple device like the Sawbench, so logically there are more questions, more things to discuss, and more price and feature negotiations. We just didn’t know how much more, exactly. Thank you for your understanding.

ST4 woodboard

It’s been a while since anything was mentioned about the upcoming ST4 synth. So, here’s a little post to show the progress of the last months.

The ST4 wood board being operated.

The ST4 wood board being operated.

For those of you not in the know, the ST4 is a multi-channel synth that specializes in rhythm. It’s a hybrid digital/analog system that offers direct control over each track and has a powerful built-in step sequencer. It can do sampling with its on-board mic or from an external source. Samples can be manipulated into arbitrary waveforms, but also standard saw, square and sine waveforms may be used. Noise generators, a wealth of envelopes and per-channel multi-mode filters allow for powerful percussive sculpting.

Our goal is to make this as much a stand-alone system as possible. There’s the usual MIDI connectivity, but there’s also the built-in step sequencer on a large display with full USB keyboard and mass storage support. This makes the ST4 a unique device and as much a studio work horse as something you can take along to your friends or use on stage. The analog VCFs and VCAs give it a warm finish. It’s a Tasty Chips synth: high character and fun to use. 🙂

The current prototype is nailed to a wood board for stability and now has its own AC/DC converter PCB. Almost everything is now on PCB’s (8 in total) and the display is fully integrated into the system. TODO: photo

The GUI is getting more mature by the day. There are little animations for when knobs are turned, the editor allows block functions for copy/paste, transpose, panning, etc. There’s still a lot to be done, but progress is rapid. TODO: anim gif

In terms of performance we can say that the audio quality is as it should be. Also the graphics performance was radically boosted (basically an optimized and specialized version of the UTFT library), and the USB Host driver was completely turned into statemachines, to allow decent multitasking without blocking waits. If anybody is interested in such code for the Arduino Due, just mail us!

There is one performance issue left, however. The potentiometers are spiky, which causes all kinds of glitches in the system. There are ways to reduce this, but we probably need some more weeks to clean this all up. Electro-Magnetic Compatibility (EMC) is a huge can of worms!

To summarize, the ST4 looks like it’s going to be a great product. We aim to release it before Christmas and we might do a Kickstarter before that time.

Kickstarter finally over. Sawbench now in the webshop!

The last sawbenches have now shipped. This also includes the custom edition (with better components and custom artwork), as shown in the picture!

Custom unit for Benjamin Bacon's Dogma Lab. Logo's were CNC milled and filled with nailpolish.

Custom unit for Benjamin Bacon’s Dogma Lab. Logo’s were CNC milled and filled with nailpolish.

And.. The Sawbench is now finally available from the shop: Sawbench product link !!

The near future: we’ll keep selling the Sawbench (as long as our stocks last) and naturally we’ll support all of the buyers and Kickstarter backers. In the next days the kit products will also become available in our webshop. We’ll also put the firmware sources online and a firmware update might also be coming up soon.

Stay tuned!


Sawbench update: 120x PCB’s, casing, planning

The electronics

This week the 100 analog and 100 digital sawbench PCB’s finally arrived. We already had 20 before and these are now fully soldered and tested. The PCB’s seem fine: the silkscreens are now DIY-proof (all values are printed).

There’s one set back: the snap-in holes of the potentiometers aren’t big enough. In the past it’s been hit or miss. Either they are just right or too small. The supplier seems unable to tell us what’s up with that. Our guess is, it’s not a very accurate process. Not as critical as the rest of the PCB. The holes in the EAGLE drawings are small too. Seems like a lucky accident that they sometimes end up being bigger.. Oh well, next time we’ll change the diameters. For now, it’s manually re-drilling 1200 holes (!!!). This is a day of work, so nothing to worry about, except a sore thumb. 😉

100 analog and 100 digital boards.. arrived yesterday.

100 analog and 100 digital boards.. arrived yesterday.

The casing

The casing design will be finalized today. And we can say it looks fantastic! An early version:

Preview of the frontplate graphics.

Preview of the frontplate graphics (pots and buttons are not shown here).

The graphics will be inverse. The background will be aluminium and the font and drawings in blue. The best news is that the colour will be integrated into the aluminium skin, making it scratch-proof and solvent-proof!

Honestly, we cannot wait to get our hands on these casings, but it will have to wait for a bit. Read on..

The planning

There have been some questions about the delivery schedule..

First of all, Kickstarter informs us of a 14 day period to collect all the pledges. This would (ideally) mean we’ll have the money by April 16th.. and can then start paying for casing fabrication.

The way it looks now the bare bones kits will be able to ship this month (April). We have enough PCB’s and a small batch of potentiometers should arrive in a few days.

Casing production (of 200 units) will take 4 weeks in total, and can only start when the Kickstarter money is in: it’s the most expensive part of the product.. We’re trying to get the first 100 casings before the end of the month, but we don’t know yet if this is possible. We’ll update this post when we know more.. Worst case estimate is that we can start assembling the full units from May 14th onwards.

  • April 15th: barebones kits start shipping
  • April 15th: first batch of potentiometers should arrive
  • April 16th: Kickstarter money should be transferred
  • April 16th: start of casing production
  • April 30th: (POSSIBLY) first casings should be available
  • April 30th: (POSSIBLY) the first 10 cased units may be shipped out!
  • May 8th: final batch of potentiometer knobs should arrive
  • May 14th: casing production done
  • May 19th: final batch of potentiometers should arrive
  • May 20th: shipping of kit+casing and full unit should commence

Feature-complete spaghetti

Loads of things have come our way. Loads of things non-synth. And this took time, loads of time. But here it is, in all its glory: a more-or-less feature-complete model of the ST4:

Feature-complete model of the ST4 in spaghetti form.

Feature-complete model of the ST4 in spaghetti form.



There’s no display connected since it couldn’t possibly fit amidst all this wiring terror, but for the rest, everything just works:

  • All four voices multi-mode VCF action
  • All filters are fully hands-on controllable per voice
  • All four stereo voices VCA action including panning per voice
  • The three ADSR envelopes and two LFO’s are fully controllable
  • Sampling and bitcrushing, voice detuning, voice modes
  • Everything can be controlled by MIDI as well
Action shot of the expansion board.

Action shot of the expansion board.

Next steps are improving performance (loose wires give a bunch of crosstalk, it’s unholy), adding the display and just replacing all that breadboard with a decent PCB… and putting it all in some preliminary casing.

Polysynth development and the Arduino Due, part due

So much has happened in the recent weeks.. Where to start?

First off, we’re making a new synth. A full-blown polyphonic, with loads of special features you’re unlikely to encounter in any other device. This time not only intended as a demonstrator, but as a unit suitable for mass production, and as portable and sturdy as you can imagine. This project is a collaboration between Tasty Chips and STU.

We don’t want to reveal too much, but we can say it’s getting there. We’re building all of this around the Arduino Due, much like the TCE-1M. The Due is so powerful that it can do 8 polyphonic voices with multiple oscillators per voice. For this synth, though, we want to keep it limited to 4 and leave some room for other more exotic features.

PWM + low-pass filter = DAC

The Due has PWM, which is faster and potentially has more resolution than the Uno. As told in previous posts it’s no problem to crank it up to 300 kHz 8 bit.. or 20 kHz 12 bit. Combining two PWM pins using carefully picked resistors, it’s possible to make 2 x 8 = 16 bit DAC’s, using a simple analog anti-aliasing filter behind it.

The Due’s SAM3X micro controller is a true powerhouse. Almost all of its pins are multiplexed, which means they have multiple functions. It turns out you can have way more than the 12 advertised PWM’s. In reality, you can have 4 more.. and now comes the best part.. all of them have complementary pins. That’s normally used for H-bridges and power electronics control where pulses should be complementary but non-overlapping.

Complementary PWM signals with “dead time”.

This non-overlap is controlled by so-called “dead time”. And this dead time is a user-specified variable per pin. So, just set your PWM complementary pair to 50% and vary the dead time on both. you lose 1 bit of resolution, but you gain 14 additional PWM pins. This means you can have a total of 15 audio DAC’s excluding the two already onboard DAC’s. How’s that for a digital oscillator bank!

Of course, all of this should be tested in detail. Using the PWM DAC’s in 8 bit mode was a
success, but there might still be problems with making it 16 bit. We’ll just have to see.

In any case, the SAM3’s PWM power is the reason we stayed Atmel/Arduino, instead of going for the hugely popular STM32. STM32 is multiplexed in a way that does not allow usage of SPI alongside PWM. Very disappointing for an otherwise great micro controller. You just need PWM’s if you’re going to do anything with analog synthesizers. There’s just no way around it.

Atmel SAM3X – The Powerhouse

The SAM3X never ceases to amaze us. While it has bad sides (which are also amazing ;)) like pins that burn out a bit too easily, it has so many good things to make up for it. And each day we discover more. For instance.. instead of the Arduino’s digitalWrite() call to set a pin high or low, you can just write:

// digitalWrite(13,HIGH);
PIOB->PIO_SODR = 1<<27; // digitalWrite(13,LOW); PIOB->PIO_CODR = 1<<27;

A digitalWrite() call is typically 1 microsecond (!) It's direct replacement, however, is only a few cycles!! As you can see these are writes to 2 different registers. One is the Set register, the other the Clear register. This allows the programmer to use only a single write access to the bus instead of the typical read-modify-write.

DMA is the other thing that the SAM3X excels. DMA, or Direct Memory Access, was considered a luxury for a long time in the world of the PC, and for an even much longer time in the embedded world. It's an ideal solution to copy data to/from peripherals without using up costly CPU and also avoiding complex interrupt prioritization designs where timer ticks go missing and all manner of nastiness might ensue.

The SAM3's DMA comes in two flavors:
- DMAC, the standard DMA Controller: extremely flexible and fast
- PDC, the Peripheral Device Controller: slower, but very easy to use

Just about anything can be transmitted over the DMAC, and it also has 6 channels. If you want to periodically send out 32 GPIO inputs to a serial bus or dump them to a memory block. It can do that for you. If you want to send out periodic SPI commands and read back their response.. it can also do that. It can do everything. It can even do linked lists.. running a sequence of transfers completely without CPU intervention. The DMAC is just extremely powerful. More akin to what you'd like to find in your mobile hardware, than on a cheap embedded device.

The PDC is simpler and is specialized for cyclic transfers. While the DMAC is always disabled after transfers complete, you can just pass the next source and destination to the PDC in an interrupt handler. It will continue to these next addresses without any bump or delay. It is slower, but can still do a few megabyte per second. It can be used to read out the ADC periodically, drive the DACs in the same way and also to read out USB at relatively high speed.

Hardware development

Next to the digital oscillator engine, there's the design of all the hardware. 2 out of 4 PCB's have already been laid out and are being feverishly tested and coded on. The focus is on hands-on control. Getting a good, solid and direct user experience as early on in the project. In those terms, some PCB's are easier than others. One contains only a bunch of potentiometers, while others contains a host of buttons, LEDs, rotary encoders, and even a display.. yes..

The Voltage Controlled Filter (VCF) is analog. Yes, this is a hybrid synth after all. We chose to abandon the mutated Steiner-Parker filter from the TCE-1M for a new design that is
very close to signal processing theory and has everything voltage controlled: even the resonance. And of course, it is multi-mode (lo, band, hi, possibly even more). The core is realized on breadboard and it sounds fine. It can be really really resonant without going into self-oscillation. But also, it could be able to do self-oscillation for all the analog nuts out there.. if you really push it. But this is something we need to work on, still.

All-in-all, we estimate it should still take a month before a workable prototype emerges. We'll keep you updated!

More reading:
The rather excellent SAM3X user guide is available here: Atmel SAM3X User Guide

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